Infrared Spectroscopy of Wafer-Scale Graphene

TL;DR

This paper presents infrared spectroscopy measurements of wafer-scale graphene, revealing key optical and electronic properties, and demonstrating its potential for far-infrared and terahertz optoelectronic applications.

Contribution

It provides comprehensive spectroscopic analysis of wafer-scale graphene grown by different methods, linking optical features to electronic properties and doping levels.

Findings

Mid-IR absorption differs between epitaxial and exfoliated graphene.

Heavily doped graphene shows significant transmission reduction at far-infrared wavelengths.

Spectroscopy enables inference of layer number, doping, and mobility.

Abstract

We report on spectroscopy results from the mid- to far-infrared on wafer-scale graphene, grown either epitaxially on silicon carbide, or by chemical vapor deposition. The free carrier absorption (Drude peak) is simultaneously obtained with the universal optical conductivity (due to interband transitions), and the wavelength at which Pauli blocking occurs due to band filling. From these the graphene layer number, doping level, sheet resistivity, carrier mobility, and scattering rate can be inferred. The mid-IR absorption of epitaxial two-layer graphene shows a less pronounced peak at 0.37\pm0.02 eV compared to that in exfoliated bilayer graphene. In heavily chemically-doped single layer graphene, a record high transmission reduction due to free carriers approaching 40% at 250 \mum (40 cm-1) is measured in this atomically thin material, supporting the great potential of graphene in far-infrared and terahertz optoelectronics.